Force Effects of the Macro-Instability of Flow Pattern on Radial Baffles in a Stirred Vessel With Pitched-Blade and Rushton Turbine Impellers

2004 ◽  
Vol 82 (9) ◽  
pp. 1268-1281 ◽  
Author(s):  
P. Hasal ◽  
I. Fort ◽  
J. Kratena
Keyword(s):  
Flow Pattern ◽  
Stirred Vessel ◽  
Rushton Turbine

scholarly journals Investigation of Horizontal Velocity Fields in Stirred Vessels with Helical Coils by PIV

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Volker Bliem ◽  
Heyko Jürgen Schultz
Keyword(s):  
Heat Transfer ◽  
Flow Pattern ◽  
Axial Flow ◽  
Flow Fields ◽  
Horizontal Velocity ◽  
Heat Transfer Area ◽  
Stirred Vessel ◽  
Rushton Turbine ◽  
Helical Coils ◽  
Improved Design

Horizontal velocity flow fields were measured by particle image velocimetry for a stirred vessel with baffles and two helical coils for enlargement of heat transfer area. The investigation was carried out in a cylindrical vessel with flat base and two different stirrers (radial-flow Rushton turbine and axial-flow propeller stirrer). Combined velocity plots for flow fields at different locations are presented. It was found that helical coils change the flow pattern significantly. Measurements for the axial-flow Rushton turbine showed a strong deflection by the coils, leading to a mainly tangential flow pattern. Behind baffles large areas of unused heat transfer area were found. First results for the axial-flow propeller reveal an extensive absence of fluid movement in the horizontal plane. Improved design considerations for enhanced heat transfer by more compatible equipment compilation are proposed.

CFD research on the influence of geometry characteristic on flow pattern and the transition mechanism in Rushton turbine stirred vessels

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Yinghui Wang ◽  
Lin Hao ◽  
Zhenxing Zhu ◽  
Jinjie Xu ◽  
Hongyuan Wei
Keyword(s):  
Flow Pattern ◽  
Turbulence Models ◽  
Stirred Vessel ◽  
Rushton Turbine ◽  
Stirred Vessels ◽  
Transition Mechanism ◽  
Flow Pattern Transition ◽  
Actual Space ◽  
Geometry Characteristic ◽  
The Relationship

Abstract In this paper, the transient MRF approach coupled with the standard k-ε and SST k-ω turbulence models was employed to study the effect of bottom shape, impeller diameter (D J) and bottom height (H 2) on critical impeller off-bottom clearance (C). It was found the bottom shape and bottom height (H 2) have obvious influence on the flow pattern transition from double-loop to single-loop of RT impeller. The flow pattern transition mechanism was inferred to relate to the relationship between the space required by the lower circulation zone and the actual space. The boundary conditions of critical C were further concluded to help distinguish the flow pattern and receive the expected one in the stirred vessel design.

Effect of the turbulence models on Rushton turbine generated flow in a stirred vessel

2011 ◽  
Vol 1 (4) ◽  
Author(s):  
Wajdi Chtourou ◽  
Meriem Ammar ◽  
Zied Driss ◽  
Mohamed Abid
Keyword(s):  
Dissipation Rate ◽  
Stokes Equations ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Stirred Vessel ◽  
Rushton Turbine ◽  
Numerical Predictions ◽  
Volume Method

AbstractIn this paper, we performed a comparison of four turbulence models using for numerical simulation of the hydrodynamic structure generated by a Rushton turbine in a cylindrical tank. The finite volume method was employed to solve the Navier-Stokes equations governing the transport of momentum. In this study four closure models tested were: k-ɛ standard, k-ɛ RNG, k-ɛ Realizable and RSM (Reynolds Stress Model). MRF (Multi Reference Frame) technique was used with FLUENT software package. The present work aimed to provide improved predictions of turbulent flow in a stirred vessel and in particular to assess the ability to predict the dissipation rate of turbulent kinetic energy (e) that constitutes a most stringent test of prediction capability due to the small scales at which dissipation takes place. The amplitude of local and overall dissipation rate is shown to be strongly dependent on the choice of turbulence model. The numerical predictions were compared with literature results for comparable configurations and with experimental data obtained using Particle Image Velocimetry (PIV). A very good agreement was found with regards to turbulence.

scholarly journals CFD Prediction of Gas-Liquid Flow in an Aerated Stirred Vessel Using the Population Balance Model

2014 ◽  
Vol 35 (1) ◽  
pp. 55-73 ◽  
Author(s):  
Zbyněk Kálal ◽  
Milan Jahoda ◽  
Ivan Fořt
Keyword(s):  
Size Distribution ◽  
Bubble Size ◽  
Water System ◽  
Population Balance ◽  
Bubble Size Distribution ◽  
Balance Model ◽  
Stirred Vessel ◽  
Rushton Turbine ◽  
Size Groups ◽  
Gas Liquid Flow

Abstract The main topic of this study is the experimental measurement and mathematical modelling of global gas hold-up and bubble size distribution in an aerated stirred vessel using the population balance method. The air-water system consisted of a mixing tank of diameter T = 0.29 m, which was equipped with a six-bladed Rushton turbine. Calculations were performed with CFD software CFX 14.5. Turbulent quantities were predicted using the standard k-ε turbulence model. Coalescence and breakup of bubbles were modelled using the homogeneous MUSIG method with 24 bubble size groups. To achieve a better prediction of the turbulent quantities, simulations were performed with much finer meshes than those that have been adopted so far for bubble size distribution modelling. Several different drag coefficient correlations were implemented in the solver, and their influence on the results was studied. Turbulent drag correction to reduce the bubble slip velocity proved to be essential to achieve agreement of the simulated gas distribution with experiments. To model the disintegration of bubbles, the widely adopted breakup model by Luo & Svendsen was used. However, its applicability was questioned.

Characterisation of Isolated Mixing Regions in a Stirred Vessel

2008 ◽  
Vol 6 (1) ◽  
Author(s):  
Mohamed Nabil Noui-Mehidi ◽  
Naoto Ohmura ◽  
Jie Wu ◽  
Bon Van Nguyen ◽  
Nami Nishioka ◽  
...  
Keyword(s):  
Digital Image Analysis ◽  
Period Doubling ◽  
Physical Space ◽  
Reynolds Numbers ◽  
Flow Structures ◽  
Stirred Vessel ◽  
Low Reynolds Numbers ◽  
Rushton Turbine ◽  
Torque Measurements ◽  
Impeller Type

An experimental study of isolated mixing regions (IMRs) in a cylindrical vessel stirred by three different impellers (a six-blade Rusthon turbine, a four-blade Lightnin A315 impeller and an axial CPE RTF4 impeller) has shown the existence of IMRs in all three systems at low Reynolds numbers. Calculations of the Re ranges in which IMRs exist, torque measurements and flow visualizations enabled the analysis of the effects of impeller type and the flow structures when IMRs were present. Particular attention was given to the case of the Rushton turbine, where digital image analysis revealed that the mechanism of IMR disappearance can be described as a period-doubling locus in the physical space, in which IMRs completely disappear at a critical Re, resulting in global mixing.

Power Consumption of Polymer Solutions in a Stirred Vessel Powered by an Hyperboloid Impeller

2001 ◽  
Author(s):  
Adélio S. Cavadas ◽  
Fernando T. Pinho
Keyword(s):  
Power Consumption ◽  
Aqueous Solutions ◽  
Xanthan Gum ◽  
Polymer Solutions ◽  
Reynolds Numbers ◽  
Newtonian Fluids ◽  
Solution Flow ◽  
Stirred Vessel ◽  
Concentrated Aqueous Solutions ◽  
Rushton Turbine

Abstract Measurements of power consumption in stirred vessel flows powered by a Rushton and an hyperboloid impeller were carried out. The fluids were aqueous solutions of tylose, CMC and xanthan gum at weight concentrations ranging from 0.1% to 0.6% and also included Newtonian fluids. For the Rushton turbine flows the addition of polymer increased the Newton number by about 13–20% at Reynolds numbers in the range 1,000–3,000, whereas with the hyperboloid impeller the Newton number decreased about 13%. This decrease was especially noticeable for the CMC solutions and was absent from the 0.2% tylose solution flow. Concentrated aqueous solutions of CMC (5.2%) and XG (3.6%) were also produced to determine the characteristic impeller parameter k for the hyperboloid, following the procedure of Metzner and Otto (1957) which was found to be 48 ±16.

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